While cases have been largely mild, scientists like Dr. Jesse Goodman, an infectious disease physician at Georgetown University and former FDA official, warn it could evolve and become more dangerous.  "This is like some brush burning around your house," he says. "You better pay attention because it could turn into something else."

The majority of human infections have come from close contact with infected animals, so risk to the public is still considered low. But the virus raises questions about how the U.S. may prepare for the possibility of another pandemic.